"Change the Batteries"

hi, use alkaline, lithium batteries or high capacity nimh batteries
this should we have tried and it works , hope it works for you also

I would try cleaning the battery terminals with a swap and a bit of rubbing alcohol.
See if that helps. Just a suggestion. Maybe the battery terminals are dirty.

Try to clean and adjust the battery springs.see more details here
Why my camera keeps saying ‘change battery’ even with new batteries?

Are you still using alkaline batteries? If so, alkaline batteries just don't have the power for more than a few pictures in a digital camera. Some may also have reached their shelf life, and though right out of the package may even have problems just powering startup of the camera. Digital cameras that use AA's for the most part should only be used with rechargeable NiMH batteries. If you read the camera's instruction manual concerning batteries, you may see the same recommendation.

Keep in mind rechargeable NiMH batteries will save you money in the long run over alkalines, AND they'll last for at least 100 pictures per charge (and probably many many more). You'll be very pleased with their performance, and may be angry with yourself for not buying them sooner. When at the store, look on the package for a power rating of at least 2500 mah.

The solution is to change the small 'date/time' battery. You can have the regular batteries as charged as you like, it won't make any difference. The tiny date/time battery is in the same compartment as the regular batteries, on the opposite side of the hinge. Extract it with a fingernail, it is situated on the left hand wall of the battery compartment (when the camera is inverted and the compartment open).

1. clean and adjust the springs in the battery compartment
2. use the right batteries, alkaline or NiMH, etc.

this tips may help
Why my camera keeps saying ‘change battery’ even with new batteries?

try new Alkaline batteries or fully charged NiMH batteries, you may need to clean and adjust the springs in the battery compartment
this tips may give you more details
http://www.myfixtips.com/blog/digital-camera/why-my-camera-keeps-saying-%e2%80%98change-battery%e2%80%99-even-with-new-batteries-176.htm

Are you still using alkaline batteries? If so, alkaline batteries just don't have the power for more than a few pics in a digital camera. Some may have reached their shelf life, and though brand new, may even have problems just powering startup of the camera. Digital cameras for the most part should only be used with rechargeable NiMH batteries. Retailers sell these for around $7 for a package of four (about $15-19 for the batteries with charger). Keep in mind they'll save you big bucks in the long run over alkalines, AND they'll last for at least 100 pictures per charge (and probably many many more). You'll be very pleased with their performance, and may slap yourself for not buying them sooner. When at the store, look on the package for a power rating of at least 2500 mah.

I have this problem as well. I thought it was a problem with my NiMH batteries. So, I bought a volt meter to make sure the batteries worked. I have 8 AA NiMH batteries. I charged them all up and tested them with the volt meter. They were all good to go. However, no matter what I put in the camera one of two things happens:
1. I get the "change batteries" message.
2. I don't get the message, but the next time I check the camera (a few days later), one of them is totally drained.
Something is very wrong and I plan on contacting Canon.

It occurred lately with reloadable NiMh-batteries.
When I put in some alkaline batteries I had no problem.
I cleaned the contact surfaces of the NiMh-batteries and the contact surfaces in the camera. Up till now I have had no problems.
grt.
Aad